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Isolation and characterization of a streptomycin resistance plasmid from Pseudomonas cepacia
Abstract:
A plasmid, Rms425, mediating resistance to streptomycin(Sm) and mercury(Hg) was isolated from Pseudomonas cepacia GN11131 of clinical origin. Rms425 was transferred to Pseudomonas cepacia, Pseudomonas aeruginosa and Escherichia coli strains by transformation with purified DNA and by conjugation between isogenic strains of P. aeruginosa or of E. coli by mixing on membrane filters. The molecular weight of Rms425 was estimated to be about 32 megadaltons by electron microscopy and it was classified as incompatibility group P. Examining the incorporation of [gamma-32P] or [8-14C] from isotope-labelled ATP into Sm using the cell-free extracts from P. cepacia or E. coli strains harboring Rms425, we found that the Sm resistance conferred by Rms425 was due to the phosphorylation of the drug.
Insights
A novel plasmid, Rms425, confers resistance to streptomycin and mercury in bacteria. This resistance is achieved through the drug phosphorylation mechanism, as demonstrated in Pseudomonas and E. coli strains.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Antibiotic resistance and heavy metal contamination pose significant public health threats.
- Plasmids are key vectors for the spread of antimicrobial and heavy metal resistance genes among bacteria.
Purpose of the Study:
- To isolate and characterize a plasmid conferring resistance to streptomycin and mercury.
- To elucidate the mechanism of streptomycin resistance conferred by the plasmid.
Main Methods:
- Isolation of plasmid Rms425 from clinical Pseudomonas cepacia.
- Transfer of Rms425 via transformation and conjugation to recipient bacterial strains (Pseudomonas and E. coli).
- Estimation of plasmid molecular weight using electron microscopy and determination of incompatibility group.
Main Results:
- Plasmid Rms425 (approx. 32 Mdal, IncP) mediated resistance to streptomycin and mercury.
- Rms425 was successfully transferred to Pseudomonas cepacia, Pseudomonas aeruginosa, and Escherichia coli.
- Streptomycin resistance resulted from the phosphorylation of streptomycin, catalyzed by enzymes encoded by Rms425.
Conclusions:
- The plasmid Rms425 is a significant genetic element mediating co-resistance to streptomycin and mercury.
- The mechanism of streptomycin resistance involves drug phosphorylation.
- Rms425 has the potential to spread resistance traits within and between bacterial species.